Present invention relates to programmed controllers, particularly those controllers that operate with processes and/or electromechanical devices. More particularly, the invention relates to verification of proper operation of such programmed controllers.
Many control devices have diverse checking systems, for example, in transmitting control characters between a controller and a controlled device, the controlled device often can send back a verification of the received command either by a special code or by a replica of the command. While this verification assures adequate transmission between a controller and a controlled device, it does not ensure that the programmed controller itself has been properly functioning.
In many programmed control devices, access keys are used to verify that access to a particular portion of memory, for example, is authorized. This access control prevents inadvertent access to critical portions of memory. Such access keys do not ensure that once memory is accessed, that the proper sequence of operation has been appropriately performed.
Also, check symbols, etc. have been used for identifying accessing mechanisms for security purposes. Again, while this does protect devices from improper controls in a limited sense, it does not ensure that the accessing mechanism is properly executing its control functions.